could oil
Regular verb: oil - oiled- oiled

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could oil
you could oil
she could oil
we could oil
you could oil
they could oil 	I could be oiling
you could be oiling
she could be oiling
we could be oiling
you could be oiling
they could be oiling	I could have oiled
you could have oiled
she could have oiled
we could have oiled
you could have oiled
they could have oiled	I could have been oiling
you could have been oiling
she could have been oiling
we could have been oiling
you could have been oiling
they could have been oiling	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't oil
you couldn't oil
she couldn't oil
we couldn't oil
you couldn't oil
they couldn't oil 	I couldn't be oiling
you couldn't be oiling
she couldn't be oiling
we couldn't be oiling
you couldn't be oiling
they couldn't be oiling	I couldn't have oiled
you couldn't have oiled
she couldn't have oiled
we couldn't have oiled
you couldn't have oiled
they couldn't have oiled	I couldn't have been oiling
you couldn't have been oiling
she couldn't have been oiling
we couldn't have been oiling
you couldn't have been oiling
they couldn't have been oiling	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I oil?
could you oil?
could she oil?
could we oil?
could you oil?
could they oil? 	could I be oiling?
could you be oiling?
could she be oiling?
could we be oiling?
could you be oiling?
could they be oiling? 	could I have oiled?
could you have oiled?
could she have oiled?
could we have oiled?
could you have oiled?
could they have oiled? 	could I have been oiling?
could you have been oiling?
could she have been oiling?
could we have been oiling?
could you have been oiling?
could they have been oiling? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I oil?
couldn't you oil?
couldn't she oil?
couldn't we oil?
couldn't you oil?
couldn't they oil? 	couldn't I be oiling?
couldn't you be oiling?
couldn't she be oiling?
couldn't we be oiling?
couldn't you be oiling?
couldn't they be oiling? 	couldn't I have oiled?
couldn't you have oiled?
couldn't she have oiled?
couldn't we have oiled?
couldn't you have oiled?
couldn't they have oiled? 	couldn't I have been oiling?
couldn't you have been oiling?
couldn't she have been oiling?
couldn't we have been oiling?
couldn't you have been oiling?
couldn't they have been oiling?